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Background <p>Bone-anchored prostheses (BAPs) address many of the shortcomings of socket prostheses, driving the adoption of the technology for lower limb amputees. However, higher femoral fracture rates have been observed in these patients compared to socket users. It is believed that this increased fracture rate is due to the direct transmission of loads to bone through the bone-anchored implant. While low-impact activities, such as walking, have been extensively studied using finite element (FE) models, other more demanding low-impact activities such as ambulating on stairs and inclines remain poorly understood. Most previously reported subject-specific FE models of femurs fitted with osseointegrated implants were not validated against experimental data. The current study aimed to validate an FE modelling methodology using implanted cadaveric specimens and to calculate the fracture risk of implanted femurs during various activities of daily living.</p> Method <p>Strain responses of cadaveric femurs fitted with press-fit osseointegrated implants under load were recorded and compared to strain predicted by specimen-specific FE models created from CT data. Five different published relationships between Hounsfield units and Young’s Moduli were investigated to determine which relationship gave the most accurate model predictions. The validated FE models of the implanted femurs were later used to simulate <i>in-vivo</i> force measurements during five routine activities of daily living. Lastly, the fracture risk of the implanted femurs during these activities was quantified using factor of safety (FOS), where FOS = 1 denoted fracture was predicted at the given load.</p> Results <p>The validated FE model predicted the experimental strain responses with a coefficient of determination (R<sup>2</sup>) of 0.91 and a root mean square error (RMSE) of 81.27&#xa0;με. The FOS for the activities of daily living of individual specimens ranged from 1.8 to 5.0, with walking up an incline having the lowest average FOS (1.9) across all specimens. Compared across different environments, the average FOS for level walking (4.3) and ambulating on stairs (4.0) were similar but almost double that of ambulating on an incline (2.2).</p> Conclusion <p>Male BAP FE models predicted the experimental bone strains and suggested that peak loads during ambulation on level ground, stairs, and inclines are unlikely to cause bone fracture.</p>

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Femoral fracture risk in transfemoral amputees with bone-anchored prosthetic limbs during activities of daily living

  • 期刊论文

  • 出版模式：

    开放获取

  • 发表日期：

    2025年11月7日

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  • Ryan Tiew,
  • Hans A. Gray,
  • Dale L. Robinson,
  • Karolina Siwicka,
  • David C. Ackland,
  • Peter V. S. Lee

摘要

Background

Bone-anchored prostheses (BAPs) address many of the shortcomings of socket prostheses, driving the adoption of the technology for lower limb amputees. However, higher femoral fracture rates have been observed in these patients compared to socket users. It is believed that this increased fracture rate is due to the direct transmission of loads to bone through the bone-anchored implant. While low-impact activities, such as walking, have been extensively studied using finite element (FE) models, other more demanding low-impact activities such as ambulating on stairs and inclines remain poorly understood. Most previously reported subject-specific FE models of femurs fitted with osseointegrated implants were not validated against experimental data. The current study aimed to validate an FE modelling methodology using implanted cadaveric specimens and to calculate the fracture risk of implanted femurs during various activities of daily living.

Method

Strain responses of cadaveric femurs fitted with press-fit osseointegrated implants under load were recorded and compared to strain predicted by specimen-specific FE models created from CT data. Five different published relationships between Hounsfield units and Young’s Moduli were investigated to determine which relationship gave the most accurate model predictions. The validated FE models of the implanted femurs were later used to simulate in-vivo force measurements during five routine activities of daily living. Lastly, the fracture risk of the implanted femurs during these activities was quantified using factor of safety (FOS), where FOS = 1 denoted fracture was predicted at the given load.

Results

The validated FE model predicted the experimental strain responses with a coefficient of determination (R2) of 0.91 and a root mean square error (RMSE) of 81.27 με. The FOS for the activities of daily living of individual specimens ranged from 1.8 to 5.0, with walking up an incline having the lowest average FOS (1.9) across all specimens. Compared across different environments, the average FOS for level walking (4.3) and ambulating on stairs (4.0) were similar but almost double that of ambulating on an incline (2.2).

Conclusion

Male BAP FE models predicted the experimental bone strains and suggested that peak loads during ambulation on level ground, stairs, and inclines are unlikely to cause bone fracture.